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Biomedical subjects

D K Sorensen

Publications and source records attributed to D K Sorensen.

At least 19 recordsLinked to original sources
PubMed1988

Evaluation of the stable fly (Stomoxys calcitrans) as a vector of enzootic bovine leukosis.

Experiments reported here were directed at 2 questions: (1) Can the stable fly (Stomoxys calcitrans) transmit enzootic bovine leukosis? (2) Could early viremia augment the probability of transmission by this insect? In one vector experiment, calves and bovine leukemia virus (BLV)-infected cows were housed with and without stable flies. The calves were monitored serologically during a 3-month postexposure period, using the agar gel immunodiffusion test. All fly-infested and fly-free calves remained BLV-seronegative. For a second vector experiment, donor calves, newly injected with blood from BLV-infected cows with high virus expression, were tethered alternately between uninoculated, weaned BLV-seronegative calves. These groups were housed with or without flies in 2 replicate trials. The inoculated calves from the first replicate seroconverted at 16 and 23 days after inoculation; the inoculated calves from the second replicate seroconverted at 11, 16, 16, and 37 days after inoculation. All uninoculated calves remained BLV-seronegative. In a manual transmission experiment, 50 unfed stable flies were allowed to complete a meal on each of 3 BLV-seronegative calves after feeding on a BLV-seropositive cow with high (42%) virus expression. One control calf was injected with blood from the cow. Seroconversion occurred in the control calf and 1 calf on which flies were given access. A scanning electron microscopic study was made of the everted and closed mouth parts of the stable fly. Given the lymphocyte count in blood from the cow used in the manual vector transmission experiment, it was calculated that 3,950 mouth part volumes would be necessary to transmit BLV.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Failure to demonstrate transmission of enzootic bovine leukemia virus infection from cows to sheep by use of common injection needles.

Four bovine leukemia virus (BLV)-seropositive and 2 BLV-seronegative cows were used as donors in a study to provide evidence whether IM injection with common needles is a means of spreading bovine leukemia. Sheep were used as recipients. Of the 4 BLV-seropositive cows, 2 had high virus expression (VE; 43% and 28% of their lymphocyte thin sections had associated BLV-particles), whereas the other 2 cows did not have observed VE. After each of the 4 cows was given an injection of a 5-antigen Leptospira bacterin, a BLV-seronegative sheep was immediately given an injection of the same bacterin with the same needle. None of these sheep seroconverted, nor did either of 2 sheep given only the bacterin (with a previously unused needle). Sheep inoculated IM with 0.2 ml of whole blood from both of the cows with high VE and from 1 of the 2 BLV-seropositive cows that did not have observed VE did seroconvert. In contrast, the sheep inoculated with 0.2 ml of blood from the remaining BLV-seropositive (0% VE) cow and from the 2 BLV-seronegative cows remained seronegative. These results were interpreted to indicate that the quantity of infective lymphocytes passed during injection with common needles is too small to induce infection.

Animals↗
PubMed1987

In vitro viral expression as a criterion for development of control procedures for enzootic bovine leukosis.

In a university beef herd of 304 cattle in which six died of lymphosarcoma between 1980 and 1984, 77% of the Angus and 26% of the Charolais cattle were determined to be infected with bovine leukemia virus (BLV). Changes in iatrogenic procedures were initiated as early control measures. In vitro viral expression (VE) was used as a criterion to identify cattle for subsequent segregation or culling. This involved determinations of percentages of BLV-associated lymphocyte profiles among thin-sectioned Ficoll-Paque-isolated blood lymphocytes that were processed into plastic after culture for 48 h. Cattle retained until completion of nutritional studies or as breeding stock were separated into two groups. The BLV-seronegative cattle, BLV-seropositive cattle with 0% VE, and BLV-seropositive cattle with 1% to 4% VE were placed in group 1. Seropositive cattle with greater than or equal to 5% VE were placed in group 2. In 1985, evaluation of in vitro VE in 108 mature BLV-seropositive cattle retained for breeding revealed 36 (33%) had no observable VE. In 1986, 58 of 108 cattle were available to be reexamined, and 21 (36%) had 0% VE in both years. The VE expression values for individual cattle were generally comparable over the 2-year period. Of 48 initial seronegative breeding stock housed in group 1 with BLV-seropositive cattle with low or no VE, 21 (44%) seroconverted during 1985 to 1986. A positive correlation of 0.585 was found between VE and age-related absolute lymphocyte number.

Animals↗
PubMed1986

Epidemiologic study of Holstein dairy cow performance and reproduction near a high-voltage direct-current powerline.

The development and operation of a high-voltage direct-current (HVDC) transmission line in rural Minnesota generated public concern over potential adverse effects to nearby residents and their livestock. Electrical environmental parameters near an HVDC line decline rapidly with distance, but effects on ambient space charge have been detected out to 1 mile. Previous studies of powerline effects on livestock have involved the more common alternating-current (HVAC) lines, which create a different electrical environment. To identify potential adverse effects of HVDC line operation on livestock, case-control and cohort study methods were used to examine various indices of Holstein performance in relation to distance from the line and the onset of line operation. It was believed that these indices would reflect changes in physiologic function or overt health effects that might arise from the HVDC environment. High-quality performance data from existing Dairy Herd Improvement Association (DHIA) records were obtained for 97% of qualifying herds located within 10 miles of the line. The large number of animals and years of observation provided high statistical power to detect even small systematic changes in performance. No significant differences in milk production or reproductive capacity were associated with presumed exposure to the HVDC environment. The absence of measurable effects in a large "sentinel" animal population may have implications for the assessment of human health risks related to HVDC transmission lines.

Abortion, Veterinary↗
PubMed1983

Infectivity in sheep of blood lymphocytes from bovine leukemia virus-infected cows with different nuclear pocket prevalences.

The infectivity for the bovine leukemia virus (BLV) of bovine blood lymphocytes, with varying lymphocyte nuclear pocket (LNP) prevalence, was studied by intradermal injection of buffy coat leukocytes from cows into sheep. Thirty-five sheep were assigned to 3 groups of 9, 11, and 15, respectively, as recipients of blood leukocytes from individual cows as follows: 9 leukocyte donor cows included 3 BLV-seropositive cows with high (greater than or equal to 2.0%) LNP prevalence (group 1); 3 BLV-seropositive cows with low (less than 0.5%) LNP prevalence (group 2); and 3 BLV-seronegative cows with increased (greater than or equal to 0.5%) LNP prevalence (group 3). The 9 sheep in group 1 became BLV-seropositive by postinoculation day (PID) 57 as determined by the agar-gel immunodiffusion test; 2 of 11 sheep in group 2 became agar-gel immunodiffusion seropositive by PID 40; none of the 15 sheep of group 3 became seropositive by PID 92. Seemingly, there is a real difference in infectivity among BLV-seropositive cattle which is related to LNP prevalence, and seronegative cattle with increased LNP prevalence may be noninfectious, ie, were not carrying covert BLV virogene.

Animals↗
PubMed1978

Frequency of lymphocytes bearing Fc receptors and surface membrane immunoglobulins in normal, persistent lymphocytotic and leukemia cows.

Fluoresceinated, heat-aggregated bovine immunoglobulins (B-IgG) and human immunoglobulins (H-IgG) were used to detect a receptor for the crystallizable fragment (Fc) of the immunoglobulin molecule on peripheral blood lymphocytes (PBL) of cattle. The aggregated and B-IgG and H-IgG bound to the bovine PBL, but aggregated H-IgG was found to be more sensitive for the detection of Fc receptors. The specificity of aggregated H-IgG binding to the Fc receptors was established by demonstrating that antigen-antibody complexes inhibited this binding, and unaggregated H-IgG did not bind significantly to PBL. Double-labeling experiments suggested that all Fc+ cells have surface immunoglobulins (SIg), a marker for B lymphocytes. The percentage of Fc+ and SIg+ cells in normal animals was 9.5% (range 4-15%) and 16.2% (range 4.5-30.2%), respectively. Persistent lymphocytotic cows had 2.71 times more Fc+ and 3.85 times more SIg+ lymphocytes than did normal cows. Cows with lymphosarcoma had a lower percentage of Fc+ and SIg+ cells than did cows with persistent lymphocytosis. Cases with thymic lymphosarcoma and those with the skin form of leukemia had normal percentages of Fc+ and SIg+ cells.

Animals↗
PubMed1977

Evidence that B-lymphocytes carry the nuclear pocket abnormality associated with bovine leukemia virus infection.

Peripheral blood lymphocytes from 3 cows with persistent lymphocytosis were separated on nylon wool columns into nylon wool-adherent and nonadherent populations. The percentage of cells coated with surface immunoglobulin (B-cells) and the frequency of lymphocytic nuclear pockets in each sub-population were then determined. In each case the adherent population consisted predominantly of B-cells with an increased nuclear pocket frequency, whereas the nonadherent cells were 98.99% negative for surface immunoglobulin (non-B-cells) and contained essentially no nuclear pockets. These findings provided additional evidence that the B-subpopulation of cells was highly involved in bovine leukemia oncogenesis.

Animals↗
PubMed1977

Detection of bovine leukemia virus in B-lymphocytes by the syncytia induction assay.

Bovine peripheral blood lymphocytes (PBL's) from 3 cows and 1 steer infected with bovine leukemia virus (BLV) were separated by fractionation through nylon wool columns into nylon-adherent and nonadherent cell populations. Nylon-adherent cells were enriched in B-lymphocytes, as determined by the presence of surface membrane immunoglobulins (slg), whereas nylon-nonadherent cells or "non-B-lymphocytes" contained few slg-bearing cells. PBL's and separated B- and non-B-lymphocyte populations were assayed for the presence of BLV by the induction of syncytia in bovine embryonic spleen cells. PBL's and B-lymphocyte populations both produced many syncytia, whereas non-B-lymphocytes yielded few or no syncytia. The specificity of syncytia formation by anti-BLV serum. PBL's from 2 control animals were negative for syncytia induction. This study presents further evidence that B-lymphocytes are the target cells for BLV infection.

Animals↗
PubMed1977

Evidence for the replication of bovine leukemia virus in the B lymphocytes.

Bovine peripheral blood lymphocytes from a cow with persistent lymphocytosis were separated on nylon wool columns into nylon-adherent and nonadherent populations. Nylon-adherent cells were highly enriched for surface immunoglobulin (SIg) bearing B lymphocytes (95.5%) and nonadherent cells for SIg negative non-B cells, presumably T lymphocytes (96.3%). The B lymphocytes were found to be the major producers for bovine leukemia virus. A total of 39% of the B-enriched cells, surviving after 72 hours in culture, produced bovine leukemia virus as compared with 0.5% of the non-B cells.

Animals↗
PubMed1976

Porcine encephalomyelitis caused by hemagglutinating encephalomyelitis virus.

Six epizootics of encephalomyeltis in suckling pigs in Minnesota were attributed to infection with hemagglutinating encephalomyelitis virus. The disease occurred in 74 litters of pigs and was characterized by sudden onset of tremors, inappetence, weakness, atazia, and hyperesthesia, with high morbidity and case fatality rate. Pathologic changes consisted of marked nonsuppurative, nondemyelinating encephalomyelitis characterized by perivascular mononuclear cuffing, gliosis, neuronal death, and satellitosis. Clinical disease was limited principally to suckling pigs during a single farrowing period and did not recur in the herds involved during the ensuing 18 months.

Animals↗
PubMed1975

The effect of penicillin, dihydrostreptomycin and prednisolone treatment of experimental Candida krusei infections of the mammary glands of dairy cattle.

The growth of Candida krusei in quarters treated intramammary with penicillin, dihydrostreptomycin and prednisolone was compared with growth in untreated quarters. No clinical mastitis occurred in any of the quarters of either group. The number of yeast organisms isolated from the quarter during and after the treatment period appeared similar in both groups. The number of leukocytes in all treated quarters increased during the antibiotic and steroid treatment period but the number of yeast isolated remained the same or decreased as compared to the control quarters.

Animals↗
PubMed1972

Prevalence and species distribution of yeast in mammary glands of dairy cows in Minnesota.

A study of the prevalence of yeast-like fungi in the mammary glands of dairy cattle was conducted in Minnesota. Quarter samples from 6,020 cows were cultured for yeast. Growth of organisms was obtained from 3.2% of the quarter milk samples. The rate of yeast infection for Minnesota dairy cattle in this study was 2.0%. The majority of the yeast isolated belonged to one of four species of the Candida genus. Candida krusei, Candida parakrusei, Candida guilliermundi, and Candida tropicalis, comprised 89% of the yeasts isolated. All of these species have been reported to cause clinical mastitis (1, 7, 9, 10, 12, 13, 15, 16). It would appear that yeast-like fungi are of sufficient prevalence in mammary glands that yeast infection would be considered in the differential diagnosis in cases of clinical mastitis.

Animals↗